This invention relates generally to inflatable restraint systems and, more particularly, to improved treatment of the emission of an inflator of such an inflatable restraint system.
Safety restraint systems which self-actuate from an undeployed to a deployed state without the need for intervention by the operator, i e., "passive restraint systems" and particularly those , restraint systems incorporating inflatable bags or cushions, as well as the use of such systems in motor vehicles have been the subjects of much discussion as the desirability of the use of such passive restraint systems has gained general acceptance in the United States.
It is well known to protect a vehicle occupant using a cushion or bag that is inflated with gas, e g , an "air bag" when the vehicle encounters sudden deceleration, such as in a collision. During deployment, the rapidly evolving gas with which the bag is typically filled is an inert gas, e.g., nitrogen. In such systems, the cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the air bag system, gas is discharged from an inflator to rapidly inflate the bag. The cushion, upon inflation, serves to restrain the movement of the vehicle occupant as the collision proceeds. In general, such air bags are commonly designed to be inflated in no more than about 30-60 milliseconds.
Vehicular inflatable restraint systems generally include multiple crash sensors generally positioned about or mounted to the frame and/or body of the subject vehicle and serve to sense sudden decelerations by the vehicle. In turn, the sensor sends a signal to an inflatable air bag/cushion module or assembly strategically positioned within the riding compartment of the vehicle to actuate deployment of the cushion. In general, an inflatable cushion provided for the protection of a vehicle driver, i.e., a driver side air bag, is mounted in a storage compartment located in the steering column of the vehicle. Whereas, an inflatable cushion for the protection of a front seat passenger, i.e., a passenger side air bag, is typically mounted in the instrument panel/dash board of the vehicle.
Typical inflatable cushion restraint systems make use of an air bag module which generally includes an outer reaction housing or canister, commonly referred to as a "reaction can" or, more briefly, as a "can". The reaction canister generally serves to support or contain other components of the air bag module system, including what is referred to as a "air bag inflator" or, more briefly, as an "inflator" or alternatively, as a "generator". The inflator, upon actuation, acts to provide the gas to inflate the air bag/cushion.
Inflators used in such systems are typically either of a pyrotechnic type or one of a variety of types of inflators such as stored gas, combustible gas or, as has become more and more common, a hybrid type inflator which types of inflators generally require gas redirection as such inflators typically discharge gas from one side or end of the inflator structure.
Pyrotechnic inflators generally contain a gas generating material which, upon initiation and activation, generates gas used to inflate the air bag/cushion. In general, the inflation gas produced by a pyrotechnic inflator is emitted from openings or emission ports along the length of the inflator.
In contrast, hybrid type inflators typically in addition to a body of ignitable pyrotechnic material generally contain, as the primary gas used for inflating the air bag, a stored, compressed gas which, upon proper actuation, is expelled from the inflator along with pyrotechnically generated gas. As a consequence of the physics associated with the storage of compressed gases, the inflator in which the compressed gas is stored typically has a cylindrical shape. Furthermore, the discharge of gas from such a cylindrically shaped gas storage container typically occurs by way of openings or emission ports at only one end of the cylindrical container. To attain proper bag deployment, however, it is generally desired that the gas is emitted into the air bag/cushion in a fairly uniform manner. This is especially desirable when the gas is discharged from only one end or side of an inflator device. With typical air bag/inflator assemblies, such uniform emission is generally attained by having a relatively even emission of gas into the deploying bag along the length of the gas inlet opening of the bag connected, directly or indirectly, to the inflator. In this way the bag is properly uniformly deployed and the risk of the bag deploying in a skewed manner due to the discharge of gas from only one end of the storage container is avoided.
U.S. Pat. No. 5,131,680 discloses a type of inflator assembly having a hybrid inflator and a diffuser. The disclosed inflator assembly includes a generally cylindrical container, a generally cylindrical diffuser, and a manifold assembly, secured to one end of the container. The diffuser is larger in diameter than the container and is mounted to encircle both the container and the manifold assembly. Further, the diffuser, which has openings through which the gas is directed to the air bag, extends substantially the entire length of the manifold assembly and a significant portion of the length of the container. Because this diffuser encircles both the container and the manifold assembly and must be able to withstand the stresses applied thereto during operation, such diffusers are generally more bulky and weighty than would be preferred.
In such and similar hybrid inflators, the burning of the pyrotechnic (gas generating) and initiation materials invariably results in the undesired production of particulate material. Various approaches have been attempted and/or suggested to deal with such particulate-containing inflator emissions.
One approach has been to simply inflate the air bag with the particulate-containing inflator emission. As a result, particulate material can be vented out from the air bag and into the vehicle. The particulate material is variously sized and typically includes a large amount of particulate within the respirable range for humans and can cause consequent respiratory problems in humans who have respired the particulate. Also, such particulate can easily become dispersed and airborne so as to appear to be smoke and thereby result in the false impression that there is a fire in or about the vehicle.
It has also been proposed to screen the gaseous emission coming from the pyrotechnic portion of such hybrid inflators. For example, the above-identified U.S. Pat. No. 5,131,680 discloses the inclusion of a circular screen "128" between the body of pyrotechnic material and the orifice through which the pyrotechnically produced emission is passed to the pressurized gas-containing chamber of the hybrid inflator.
Also, U.S. Pat. No. 5,016,914 discloses the inclusion of a filter identified as a metal disk having a plurality of suitably sized openings therein. The disk is disclosed as functioning to trap large particles such as may be present in the generated gas.
Such techniques of filtering or screening the gaseous emission of the pyrotechnic section of the hybrid inflator prior to contact with the stored, pressurized gas of the inflator generally suffer such as from undesirably slowing or preventing the transfer of heat to the stored gas. In general, in such hybrid inflators, the transfer of heat to the stored gas is desired in order to produce desired expansion of the gas. Consequently, the slowing or preventing of desired heat transfer can result in a reduction in the performance of the inflator. Also, the screening or filtering of particulate at this location within the inflator can undesirably effect gas flow within the inflator. For example, the flow of gas out of the pyrotechnic chamber and into the stored gas chamber of the inflator can be undesirably restricted, causing the pressure inside the pyrotechnic chamber to increase and thereby increase the potential for structural failure by such pyrotechnic chamber.
Thus, there is a continuing need for a safe and effective, economical apparatus and technique for particulate removal from the gaseous emission of such inflators. The removal of such particulate material can prevent, minimize or reduce any discomfort to which a vehicle occupant may be subjected to as a result of the use of such inflators in the system. Furthermore, such particulate removal can prevent safety concerns such as a vehicle occupant unnecessarily panicking when he or she, seeing particulate material having become dispersed and airborne within the vehicle, arrives at the false conclusion that the vehicle is on fire.
In addition, the temperature of the gaseous emission of inflators can typically vary between about 1000.degree. F. and 2000.degree. F., dependent upon numerous interrelated factors including the level of inflator performance being sought, as well as the type and amount of gas generant and stored gas used therein, for example. As a result of being subjected to such high temperatures, air bags made of conventional air bag materials, such as nylon or a nylon derivative, can upon deployment experience burning which in turn can increase the potential of the occupant being burned. Consequently, air bags used in conjunction therewith typically must be constructed of or coated with a material resistant to such high temperatures. For example, in order to resist such burning through of an air bag such as made from nylon fabric, the nylon fabric air bag material can be coated with neoprene or one or more neoprene coated nylon patches can be placed at the locations of the air bag at which the hot gas initially impinges. As will be appreciated, such specially fabricated or prepared air bags typically are more costly to manufacture or produce.
Thus, a system permitting the effective treatment of such high temperature gaseous emissions is desired.